Fluid regulating microvalve assembly for fluid consuming cells

ABSTRACT

A fluid regulating microvalve assembly for use to control fluid flow to a fluid consuming electrode, such as an oxygen reduction electrode, in an electrochemical cell. The microvalve assembly includes a stationary valve body having an aperture and a microactuator movable from a first position where the microvalve body aperture is closed to fluid flow to at least a second position where fluid is able to pass through the microvalve body aperture. The fluid regulating microvalve assembly can utilize cell potential or a separate source to open and close the microvalve. The fluid regulating microvalve assembly can be located outside the cell housing or inside the cell housing, for example between one or more fluid inlet apertures and the fluid consuming electrode. The invention includes a method of making a multilayer microvalve assembly, particularly one for use in a fluid depolarized battery, using a printing process to deposit at least one of the layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/522,704, filed Oct. 29, 2004.

FIELD OF THE INVENTION

The present invention relates to fluid regulating microvalve assembliesadapted to control the rate of flow of one or more fluids, particularlya gas, between an interior and an exterior of a cell housing of a cell,such as a fuel cell or battery that is preferably air-depolarized orair-assisted, as well as fuel cells and batteries containing the fluidregulating microvalve assemblies. Methods for preparing fluid regulatingmicrovalve assemblies and cells containing the microvalve assemblies aredisclosed.

BACKGROUND OF THE INVENTION

Electrochemical battery cells that use a fluid, such as oxygen or othergas(es), from outside the cell as an active material to produceelectrical energy, such as air-depolarized, air-assisted and fuel cellbattery cells, can be used to power a variety of electronic devices. Forexample, air containing oxygen enters into an air-depolarized orair-assisted cell, where it can be used as, or can recharge, thepositive electrode active material. The oxygen reduction electrodepromotes the reaction of the oxygen with the cell electrolyte and,ultimately the oxidation of the negative electrode active material withthe oxygen. The material in the oxygen reduction electrode that promotesthe reaction of oxygen with the electrolyte is often referred to as acatalyst. However, some materials used in oxygen reduction electrodesare not true catalysts because they can be at least partially reduced,particularly during periods of relatively high rate discharge.

One type of air-depolarized cell is a zinc/air cell. This type of celluses zinc as the negative electrode active material and has an aqueousalkaline (e.g., KOH) electrolyte. Manganese oxides that can be used inzinc/air cell air electrodes are capable of electrochemical reduction inconcert with oxidation of the negative electrode active material,particularly when the rate of diffusion of oxygen into the air electrodeis insufficient. These manganese oxides can then be reoxidized by theoxygen during periods of lower rate discharge or rest.

Air-assisted cells are hybrid cells that contain consumable positive andnegative electrode active materials as well as an oxygen reductionelectrode. The positive electrode can sustain a high discharge rate fora significant period of time, but through the oxygen reductionelectrode, oxygen can partially recharge the positive electrode duringperiods of lower or no discharge, so oxygen can be used for asubstantial portion of the total cell discharge capacity. This means theamount of positive electrode active material put into the cell can bereduced and the amount of negative electrode active material can beincreased to increase the total cell capacity. Examples of air-assistedcells are disclosed in U.S. Pat. No. 6,383,674 and U.S. Pat. No.5,079,106.

An advantage of air-depolarized, air-assisted and fuel cells is theirhigh energy density, since at least a portion of the active material ofat least one of the electrodes comes from or is regenerated by a fluid(e.g., a gas) from outside the cell.

A disadvantage of these cells is that the maximum discharge rates theyare capable of can be limited by the rate at which oxygen can enter theoxygen reduction electrode. In the past, efforts have been made toincrease the rate of oxygen entry into the oxygen reduction electrodeand/or control the rate of entry of undesirable gases, such as carbondioxide, that can cause wasteful reactions, as well as the rate of waterentry or loss (depending on the relative water vapor partial pressuresoutside and inside the cell), that can fill void space in the cellintended to accommodate the increased volume of discharge reactionproducts or dry the cell out, respectively. Examples of these approachescan be found in U.S. Pat. Nos. 6,558,828; 6,492,046; 5,795,667;5,733,676; U.S. Patent Publication No. 2002/0150814; and InternationalPatent Publication No. WO 02/35641. However, changing the diffusion rateof one of these gases generally affects the others as well. Even whenefforts have been made to balance the need for a high rate of oxygendiffusion and low rates of CO₂ and water diffusion, there has been onlylimited success.

At higher discharge rates, it is more important to get sufficient oxygeninto the oxygen reduction electrode, but during periods of lowerdischarge rates and periods of time when the cell is not in use, theimportance of minimizing CO₂ and water diffusion increases. To providean increase in air flow into the cell only during periods of high ratedischarge, fans have been used to force air into cells (e.g., U.S. Pat.No. 6,500,575), but fans and controls for them can add cost andcomplexity to manufacturing, and fans, even micro fans, can take upvaluable volume within individual cells, multiple cell battery packs anddevices.

Another approach that has been proposed is to use microvalves to controlthe amount of air entering the cells (e.g., U.S. Pat. No. 6,641,947 andU.S. Patent Publication No. 2003/0186099), but external means, such asfans and/or relatively complicated electronics can be required tooperate the microvalves.

Yet another approach has been to use a water impermeable membranebetween an oxygen reduction electrode and the outside environment havingflaps that can open and close as a result of a differential in airpressure, e.g., resulting from a consumption of oxygen when the batteryis discharging (e.g., U.S. Patent Publication No. 2003/0049508).However, the pressure differential may be small and can be affected bythe atmospheric conditions outside the battery.

Additional approaches utilizing microvalves to control the amount of gasentering a cell are set forth in U.S. Pat. Nos. 5,304,431; 5,449,569;5,541,016; and 5,837,394; incorporated herein by reference, wherein themicrovalves are formed utilizing a silicon or semiconductor substrateand etching, deposition and micromachining processes.

Microactuators are further described in U.S. Pat. Nos. 4,969,938;5,069,419; 5,271,597; and publications such as “Fluister: semiconductormicroactuator” described in Instruments and Apparatus News (IAN),October 1993, p. 47, and Electronic Design, Nov. 1, 1993, p. 3.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the present invention toprovide a low cost, reliable fluid regulating microvalve assembly thatis relatively inexpensive and straightforward to produce.

A further object is to provide a fluid regulating microvalve assemblythat is relatively small in size and takes up little volume in a cell inwhich the microvalve assembly is incorporated, thereby maximizing volumefor energy producing components.

Another object of the invention is to provide a cell, particularly afuel cell or battery with a fluid consuming positive electrode,preferably an oxygen reduction electrode and a fluid regulatingmicrovalve assembly that allows high rate discharge of the cell withrelatively low or even no capacity loss during periods of low rate or nodischarge.

Yet another object of the invention is to provide a multi-layermicrovalve assembly that can have a complex configuration and beefficiently and economically produced at high speeds, preferablyutilizing a printing process during at least one step utilized to formthe microvalve assembly.

Accordingly, one aspect of the invention is a microvalve assembly for anelectrochemical cell, comprising a stationary microvalve body comprisinga polymer, elastomer or rubber and an aperture located between a firstsurface and a second surface; and a movable microactuator connected tothe microvalve body and capable of moving between a first position wherefluid cannot pass through the microvalve body aperture and a secondposition which allows fluid to pass through the microvalve bodyaperture, and wherein the microactuator is thermally actuated.

Another aspect of the invention is an electrochemical cell, comprising ahousing including one or more fluid inlet apertures, a negativeelectrode, a fluid consuming positive electrode, and a microvalveassembly operatively connected to the one or more fluid inlet aperturesfor controlling passage of fluid to the fluid consuming positiveelectrode, wherein the microvalve assembly comprises (a) a stationarymicrovalve body comprising a polymer, elastomer or rubber and anaperture located between a first surface and a second surface; and (b) amovable microactuator connected to the microvalve body and capable ofmoving between a first position where fluid cannot pass through themicrovalve body aperture and a second position which allows fluid topass through the microvalve body aperture.

Yet another aspect of the invention is a method for preparing amicrovalve assembly, comprising the steps of forming a microvalve bodyhaving one or more layers; forming a microactuator having one or morelayers; and operatively joining the microvalve body to themicroactuator, wherein the microvalve body comprises an aperture thatextends through the body from a first surface to a second surface,wherein the forming of the one or more microvalve body or microactuatorlayers, or both, includes utilizing a printing process, and wherein themicroactuator is operatively connected to the microvalve body andcapable of moving between a first position where fluid cannot passthrough the microvalve body aperture and a second position which allowsfluid to pass through the microvalve body aperture.

These and other features, advantages and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification, claims and appendeddrawings.

Unless otherwise specified, as used herein, the following terms aredefined as follows:

-   -   fluid—a substance that can flow such as a liquid or a gas;    -   fluid consuming electrode—an electrode that uses a fluid from        outside the cell housing as an active material; and    -   thermally actuated microactuator—a microactuator whose motion is        caused by a change in temperature in a portion of the        microactuator.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and other features andadvantages will become apparent by reading the detailed description ofthe invention, taken together with the drawings, wherein:

FIG. 1 is a cross sectional side view of a cell including a fluidregulating microvalve assembly.

FIG. 2 is a cross sectional side view of a second cell including a fluidregulating microvalve assembly.

FIG. 3 is a cross sectional side view of one embodiment of a fluidregulating microvalve assembly.

FIG. 4A is a cross sectional side view of an embodiment of a fluidregulating microvalve assembly incorporating one alternative of alatching device wherein the microvalve assembly is in a closed position.

FIG. 4B is the cross sectional side view of FIG. 4A, wherein themicrovalve assembly is in an open position with the latch arm engagedwith the microactuator.

FIG. 5 is a schematic of one embodiment of a circuit plan including abattery, control unit, microactuator and switch.

FIG. 6 is a cross sectional side view of an embodiment of a fluidregulating microvalve assembly including two portions in position to beconnected.

FIG. 7 is a cross sectional side view of an embodiment of a fluidregulating microvalve assembly including two portions in position to beconnected, further incorporating a latching device.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment of the invention, a fluid regulating microvalveassembly is operatively connected to a cell that uses a fluid, such asoxygen or other gas or gases, from an exterior of the cell, such as thesurrounding atmosphere, as an active material for an electrode presentin the interior of the cell. The fluid regulating microvalve assemblycontrols the flow rate of fluid between the exterior and interior of thecell and ultimately the flow rate to a fluid consuming electrode, suchas an oxygen reduction electrode. The cell can be a fuel cell such as amethanol or hydrogen fueled oxygen cell, an air-depolarized cell, or anair-assisted cell as known in the art. Other possible cell typesinclude, but are not limited to, chlorine or bromine depolarized cells.Also, the microvalve assemblies of the present invention can be used in“reserve” cells where the fluid admitted into a predetermined area ofthe cell by the microvalve assembly is stored in a separate reservoiruntil required. The fluid can be a salt containing electrolyte orsolvent which will dissolve salts in the body of the cell which incombination with the salts form the electrolyte necessary for the celloperation. Similarly, cells designed to operate under water, includingsaltwater or seawater, can incorporate a microvalve of the presentinvention allowing the cell to be relatively light in weight untilplaced in the water whereby the microvalve assembly selectively admitsthe water into the cell to be used therein.

The fluid regulating microvalve assembly is configured to selectivelysupply the fluid in sufficient amounts from the exterior of the cell sothat the cell can discharge at a high rate or power level, and alsominimize or prevent the fluid from entering the interior of the cellwhen the cell is not being discharged or being discharged at anextremely low rate.

The fluid regulating microvalve assembly of the invention is describedhereinbelow with respect to air-depolarized cells, preferably utilizingan oxygen reduction electrode, but it is to be understood that themicrovalve assemblies can also be utilized with other types of fluidconsuming electrodes, such as fuel cells that can utilize one or morefluids other than oxygen, or from outside the cell housing as activematerials for one or all of the electrodes of the cell. The fluidregulating microvalve assemblies can be utilized with fluids such asseawater, particularly for an underwater application. Examples ofseawater batteries are described in U.S. Pat. No. 3,007,993 and in U.S.Pat. No. 3,943,004.

One embodiment of an air-depolarized electrochemical cell including afluid regulating microvalve assembly is a button cell, as shown inFIG. 1. The cell includes a housing with a container 11 and a cover 2and has one or more fluid inlet apertures 9 which preferably are theonly fluid communication port(s) between the interior and the exteriorof the cell housing. At least one fluid regulating microvalve assembly10 is operatively connected to the one or more apertures 9 such that,when microvalve 10 is in a closed position, fluid communication from theambient atmosphere to an oxygen reduction positive electrode located inthe interior of the cell is prevented. Likewise, when microvalveassembly 10 is in an open position, fluid communication from theexterior to the oxygen reduction positive electrode in the cell ispermitted. The cover 2 is a made from an electrically conductive metal.The metal can include a steel or stainless steel substrate. The exteriorsurface can have a layer including a metal, such as nickel or tin, thatis resistant to corrosion, and the interior surface can have a layerincluding one or more metals, such as copper, tin, zinc and alloysthereof, with a relatively high hydrogen over potential, to minimizehydrogen gas generation. The substrate metal can be plated and/or cladon one or both surfaces. For example, the cover 2 can be formed from atriclad material with a stainless steel substrate, a nickel layer on theexternal surface, and a copper layer on the internal surface, and theformed cup can optionally be plated or otherwise coated after formingwith another metal, such as tin. The container 11 can be made from anelectrically conductive metal such as steel or stainless steel, whichmay be plated with tin on one or both surfaces.

The housing also includes a gasket 3 between the adjacent side walls ofthe cover 2 and container 11 to provide a compression seal therebetweenand to electrically insulate the cover 2 from the container 11. Thegasket 3 can be made from any suitable thermoplastic material thatprovides the desired sealing properties. Material selection is based inpart on the electrolyte composition. Suitable materials for alkalinezinc-air cells include nylons, propylenes, sulfonated polyethylenes, andimpact modified polystyrenes.

The cell contains a negative electrode 1 that is adjacent to and inelectrical contact with the cover 2, which can be the negative terminalof the cell. The negative electrode includes an active material mixturecomprising an electrochemically active material, such as zinc, and anelectrolyte, preferably an aqueous electrolyte with a solute such asKOH. The zinc is preferably a low gassing zinc alloy, as described inU.S. Pat. No. 6,602,629, incorporated herein by reference, particularlywhen the cell contains no added mercury. Alternatively the zinc can be alow expansion zinc, as disclosed in U.S. Pat. No. 5,464,709,incorporated herein by reference, such as an alloy of zinc alloyed withbismuth, indium and aluminum, as disclosed in U.S. Patent PublicationNo. 2005/0106461-A1, incorporated herein by reference. The negativeelectrode mixture can be a gelled mixture, using an acrylic acid polymerin the 100% acid form (e.g., CARBOPOL® 940 or 934, available fromNoveon, Inc., Cleveland, Ohio, USA) as a gelling agent. The mixture canalso include various organic and inorganic compounds as additives, suchas additives that can reduce hydrogen gas generation in the cell.Examples of such additives include zinc oxide, indium hydroxide, and apolyethylene glycol compound (e.g., a methoxyethylene glycol such asCARBOWAX® 550, available from Dow Chemical, Midland, Mich., USA).

The cell also contains an oxygen reduction positive electrode 7, whichcan be referred to as an air electrode. In one embodiment as shown inFIG. 1, the positive electrode 7 is isolated from the container 11 suchthat electrical output is passed through the microvalve assembly 10connected in series to the positive electrode 7. In another embodiment,the positive electrode 7 is in electrical contact with the container 11,which can be the positive terminal of the cell. The positive electrode 7is a porous layer containing a reversibly reducible material thatpromotes the reaction of oxygen from outside the cell with theelectrolyte so the zinc in the negative electrode 1 can be oxidized. Inaddition, the porous layer of the positive electrode 7 can also containcarbon or graphite and a binder such as polytetrafluoroethylene.Positive electrode 7 can further include an electrically conductivemetal (e.g., nickel) screen or mesh current collector located in theportion of the positive electrode 7 adjacent to the negative electrode1. The positive electrode can also include a gas (e.g., oxygen)permeable, electrolyte impermeable membrane 5 on the surface of theporous layer facing the apertures 9. The membrane 5 can be a polymericfilm, such as a polytetrafluoroethylene film.

At least one, preferably two layers of separator 8 are disposed betweenthe negative electrode 1 and the positive electrode 7. The separator 8is a thin microporous membrane that is ion-permeable and electricallynonconductive. It is capable of holding at least some electrolyte withinthe pores of the separator 8. The separator 8 is disposed betweenadjacent surfaces of the electrodes 1, 7 to electrically insulate themfrom each other. The separator layers can be the same or differentmaterials. Suitable materials include polypropylene separators. Forexample, if two layers are used, the layer immediately adjacent to thepositive electrode 7 can be a hydrophobic polypropylene membrane, andthe other layer can be a water-wettable nonwoven polypropylene.

Located on the side of the positive electrode 7 opposite the separator 8can be a porous gas diffusion pad, to allow distribution of air enteringthe cell across the bottom surface of the positive electrode 7. This padcan be made from any suitable material, such as a sheet ofpolytetrafluoroethylene film.

Below the gas diffusion pad, between it and the inside surface of thebottom of the container 11 can be a spacer 6 with one or more cavitiestherein to accommodate the microvalve assembly/assemblies 10. The spacer6 cooperates with the container 11 and microvalve assembly 10 so theonly path for gas communication between the exterior and interior of thecell is through apertures 9 and microvalve assemblies 10.

A second gasket 4 can be disposed on the inside of container 11 toelectrically isolate positive electrode 7, if desired, such thatelectrical output is passed through microvalve assembly 10 as shown inFIG. 1. In other embodiments, microvalve assembly 10 is controlledutilizing a control circuit, and gasket 4 is absent or otherwisesituated such that positive electrode 7 is in electrical contact withcontainer 11. Materials suitable for gasket 4 include those types ofmaterials listed above as suitable for gasket 3.

FIG. 2 illustrates a further embodiment of the present invention,wherein fluid regulating microvalve assembly 15 is disposed in acylindrical cell housing. While a cylindrical cell is shown, it isunderstood by one of ordinary skill in the art that other shapes and/orsizes of cells can be utilized. For example, the cell can be a prismaticcell, having a housing with a generally rectangular or square shape. Thecell in FIG. 2 has a housing that includes a can 26 with a closed bottomand a top end, as well as a cell cover 12 and a gasket 18 disposed inthe top end of the can 26. The can 26 is in electrical contact with apositive electrode 24, located within an annular chamber, and the cover12 is in electrical contact with the negative electrode mixture 23through the microvalve assembly 15 as shown in FIG. 2. The negativeelectrode 23 is located in a cavity within the annular positiveelectrode chamber. A separator 21 is located between positive electrode24 and negative electrode 23.

The top end of the can 26 cooperates with the cell cover 12 and gasket18, as well as a sealing member 20, a structural bracing member 17 and acontact member 13 to close the top of the cell, except for one or morepassageways for fluid from outside the cell to reach the positiveelectrode chamber. The fluid passageway includes at least one fluidinlet aperture 16 in the cell cover 12 and at least one opening in thebracing member 17, and the sealing member 20 is either porous orcontains at least one hole 19. At least one microvalve assembly 15 is influid communication with the passageway(s) to selectively control fluidflow to the positive electrode 24, closing the fluid passageway(s) whenthe microvalve assembly 15 is in the closed position. When themicrovalve assembly 15 is closed, the active ingredients of the cell areeffectively sealed from the ambient atmosphere, and when the microvalveassembly is open, fluid communication from the ambient atmosphere to thedesired active portions of the cell is permitted. In one embodiment, themicrovalve assembly 15 is electrically connected to the negativeelectrode 23 and positive electrode 24 of the cell, directly oroptionally through a control circuit.

The can 26 has a bead or reduced diameter step near the top end tosupport gasket 18 and cell cover 12. Gasket 18 is compressed between can26 and cover 12 to form a seal, and a compression seal is also formedbetween the sealing member 20 and both the can 26 and the contact member13. The gasket 18 also electrically insulates the negative cell cover 12from the positive can 26.

The negative electrode 23 includes a current collector 25, which is inelectrical contact with contact member 13, and contact member 13 is inelectrical contact with cell cover 12, either directly or throughmicrovalve assembly 15. Bracing member 17 holds contact member 13 in acentered position, and when electrical contact between the contactmember 13 and the cell cover 12 is through the microvalve assembly 15,insulating cap 14 provides electrical insulation between the contactmember 13 and cell cover 12.

In one embodiment, the negative electrode 23 includes zinc as anelectrochemically active material and an electrolyte. Positive electrode24 preferably is porous and electrically conductive and includes acatalyst, such as manganese dioxide, and optionally a binder.

A decorative label 22 surrounds the outside of the can 26 except on theend where the positive terminal cover 27 covers the end of the can 26.

In general, components of the cell shown in FIG. 2 can be made frommaterials of similar compositions to the corresponding components of thebutton cell described above.

It is to be understood that additional cell parts, arrangements, or thelike may also be employed without departing from the teachings of thepresent invention. For example, the locations of the positive andnegative electrodes can be reversed; this requires correspondingrelocation of the air inlets and microvalve assemblies. Moreover, two ormore cells in one or more housings may utilize the same microvalveassembly or more than one microvalve assembly can be connected to asingle cell. The microvalve assembly can be located outside or withinthe cell housing. The fluid regulating microvalve assembly can bedesigned to be operated prior to integration into the electrochemicalcell, or otherwise be designed to begin functioning after incorporationinto the cell. In one embodiment, the cell is provided with seal over afluid inlet aperture. In another embodiment the seal is removedmanually. In a further embodiment, the microvalve assembly is providedwith a seal thereon, that is broken, perforated or split on initialactivation of the electrical device.

As described hereinabove, in an air-depolarized cell the fluidregulating microvalve assembly is operatively connected to the surfaceof the oxygen reduction electrode that is accessible to fluid (air) fromoutside of the cell, i.e., the air side, and thus is able to controlfluid access to the oxygen reduction electrode. The fluid regulatingmicrovalve assembly can be disposed in any suitable location in relationto the cell housing, i.e., operatively connected to, on, or within, aslong as the assembly is on the air side of the oxygen reductionelectrode. For example, a fluid regulating microvalve assembly can beconnected to or positioned adjacent to the inside surface of thatportion of the housing in which one or more air entry ports are located,or connected to or adjacent to the oxygen reduction electrode, connectedto another cell component such as an internal seal member, bracingmember or gas permeable sheet, on the air side of the oxygen reductionelectrode, or integrated into the case of a battery containing thecell(s).

A printing device is utilized in one embodiment to form one or morelayers or components of the fluid regulating microvalve assembly. Whilethe terms “printing” and “depositing” are utilized throughout thespecification to describe the microvalve assembly and methods of thepresent invention, it is to be understood in the broadest aspect of theinvention that at least one layer of the microvalve assembly is printedon one or more other layers. The one or more other layers of themicrovalve assembly can be printed or formed using one or more differentprocesses, and combinations thereof. The printing device can produce oneor more layers in numerous configurations at a relatively high speed ona substrate. Thus, fluid regulating microvalve assemblies of variousshapes and sizes can be mass produced in high volume. The substrate canform a portion of the microvalve assembly, such as a microvalve body, orbe removed from the printed layers of the microvalve assembly once theprinting operation has been performed. In the latter case, the printedlayers can form the microvalve assembly alone, or be used in conjunctionwith one or more other components or layers, such as a housing, to forma microvalve assembly. Any suitable printing process can be used.Examples of printing processes include indirect (offset) processes, inwhich ink is applied to a printing plate to form an image to be printed,transferred to a rubber “blanket”, and then transferred to thesubstrate, and direct processes, in which an image is transferreddirectly from an image carrier to the substrate. Lithography is anexample of an offset process, and examples of direct processes includegravure, flexography, screen printing, letterpress printing, andphotolithography. Printing processes such as ink jet and laser jetprocesses can be adapted to making a microvalve assembly. Preferredprinting processes include ink jet printing and laser jet printing.Commercially available printing devices and services can be used.Contract manufacturing and design services can be obtained fromcompanies such as First Index of Spokane, Wash. and Whippany, N.J. aswell as from Conductive Technologies, Inc. of York, Pa. and ConnectionTechnologies of Detroit Mich. Ink jet printers or printer services areavailable from REA Electronik GmbH Cleveland, Ohio, and Muehtal, Germanyas well as from Aesthetic Finishers of Piqua, Ohio. Etching services areavailable from Northwest Etch Technology of Tacoma, Wash., andFotofabrication of Chicago, Ill. Laser cutting and other services areavailable from Magni-fab Division of Wooster, Ohio, SchoonoverIndustries of Ashland, Ohio and Marian, Inc. of Indianapolis, Ind.Miniature spring or spring-like devices are available from Moyer SpringCo., Angola, Ind., or Maverick Spring Makers Limited of Brantford,Ontario, Canada.

In addition to the printing device, additional devices and processes canbe utilized in combination to produce the microvalve assembly. Forexample, devices can be utilized to create apertures or vents in one ormore layers of the microvalve assembly; to remove a portion of a layeror coating of the microvalve assembly such as by a process, but notlimited to, cutting, melting, washing, dissolving, or the like; and tojoin portions of the microvalve assembly. Accordingly, additionaldevices that can be used to prepare a microvalve assembly, individuallyor in combination, include, but are not limited to, die cutting devices,drilling devices, chemical and photochemical etching processes, anddevices such as lasers, laminating devices, machining or micromachiningdevices, or the like. Devices and processes can be utilized that washaway or melt out a portion of one or more (a) temporary layers such as afiller plug, or (b) permanent layers of the microvalve assembly tocreate a desired form such as, but not limited to, a cavity or fluidtransport channel, or a free space to allow movement of one or moreparts. One or more layers can be printed which do not adhere to parts ofthe substrate or subsequent layers so they function as parting layersallowing movement of adjacent parts. Examples of various materials andtechniques are set forth in U.S. Patent Application No. 2003/0201175,U.S. Pat. No. 5,246,730, and U.S. Pat. No. 4,830,922, herein fullyincorporated by reference.

Fluid regulating microvalve assemblies generally comprise a stationarymicrovalve body having one or more fluid apertures and a microactuator,which is movable from a closed position to an open position, therebyallowing fluid to flow through the microvalve body one or moreapertures. In one embodiment, construction of a fluid regulatingmicrovalve assembly is accomplished using a printing process to buildlayers of the microvalve assembly on a substrate. Many different typesof substrates can be utilized, including, but not limited to, metals,metal oxides, glass, polymers, rubbers or elastomers, and combinationsthereof.

Non-limiting examples of metals and metal oxide substrates comprisesilica, silicon, aluminum, iron, nickel, tin, zinc, copper, titanium andcombinations and alloys thereof, such as brasses, bronzes, stainlesssteels and shape memory alloys.

Non-limiting examples of polymers comprise polyester, polycarbonate,polystyrene, polyolefins such as polyethylene or polypropylene,polyethylene terephthalate, polyamide, polyoxides such as polyethyleneoxide, polyacrylamide, polyurethane, polyalkene, polyacrylate,polymethacrylate, polyvinyl ether, polyvinyl thioether, polyvinylalcohol, polyvinyl ketone, halogenated polymers such aspolytetrafluoroethylene (TEFLON® from DuPont) or polyvinyl halides suchas polyvinyl chloride, polyvinyl nitrite, polyvinyl ester, polyarylene,polysulfonate, polysiloxane, polysulfide, polythioester, polysulfone,polyacetal, or copolymers or combinations thereof.

Non-limiting examples of substrate rubbers or elastomers comprise or arederived from one or more same or different conjugated dienes having from4 to about 12 carbon atoms with specific examples including butadiene,isoprene, pentadiene, hexadiene, octadiene, and the like. Rubbers of thesubstrate include copolymers of the above-noted conjugated dienemonomers with one or more vinyl substituted aromatic monomers containingfrom 8 to 12 carbon atoms such as styrene, alpha-methyl styrene, t-butylstyrene, or a vinyl compound such as acrylonitrile, vinylpyridine,acrylic acid, methacrylic acid, alkyl acrylate, and alkyl methacrylate.Still further rubbers include copolymers of olefins with anon-conjugated diene (EPDM rubbers) such as ethylene propylenecyclopentadiene terpolymers,ethylene-propylene-5-ethylidene-2-norbornene terpolymers, and ethylenepropylene 1,4-hexadiene terpolymers. Further examples of suitablerubbers include polybutadiene, synthetic polyisoprene, natural rubber,styrene-butadiene rubber, EPDM rubber, nitrile rubber, halogenatedrubber, neoprene, silicone elastomers, ethylene acrylic elastomers,ethylene vinyl acetate copolymers, epichlorohydrin elastomers, and thelike, or combinations thereof.

The polymers, rubbers, or elastomers, and combinations thereof, whetherutilized in the substrate layer, or in one or more other layers of thepresent invention, independently, can include one or more of variousadditives, fillers, lubricants, stabilizers, processing aids,antidegredants, waxes, fibers that are synthetic or natural or both,mineral fibers, glass, clay, silica, compatibilizers, flame retardants,dispersing agents, colorants, and the like, which are utilized inconventional amounts as known to the art and to the literature. Examplesof natural fibers include, but are not limited to, cotton and cellulosefibers. Examples of synthetic fibers include, but are not limited to,fiberglass, polyester, polyamide both nylon and aramid, polyethylene,polypropylene, and carbon fibers.

The substrate is rigid or flexible in character. In a preferredembodiment, the substrate is a rigid sheet or film. In a preferredembodiment, the substrate has a thickness of generally from about 0.01to about 0.375 millimeters, and preferably from about 0.05 to about 0.25millimeters. In one embodiment, the substrate forms at least a portionof the microvalve body of the fluid regulating microvalve assembly andremains in a stationary position when the microvalve assemblymicroactuator is actuated between a closed position and an openposition. The substrate may be porous or non-porous to fluids, withnon-porous substrates being preferred to more accurately control theamount of fluid that passes through the fluid regulating microvalveassembly.

A fluid regulating microvalve assembly is fabricated in one embodimentas follows. One embodiment of the particular microvalve assembly isillustrated in FIG. 3. A desired substrate 62 is provided, preferablyhaving a thickness sufficient to bear the contemplated fluid pressure.The substrate 62 is perforated or cut to produce an aperture 72 throughwhich fluid will flow. When the substrate 62 utilized is of a largerarea than the desired area for the microvalve assembly, the substratemay be perforated or cut to the size of the desired microvalve assemblyto be produced.

The length, width and height dimensions of the microvalve assembly arelimited by the dimensions and desired placement in a cell, battery, orcase design. Independently, the length and width generally range fromabout 2 to about 25 millimeters, and preferably from about 5 to about 10millimeters. The size of one aperture 72 ranges generally from about 0.1to 10 millimeters, and preferably from about 0.4 to about 2 millimeters.In one embodiment, a preferred microvalve assembly is 5 millimeters inlength by 5 millimeters in width having a 1 millimeter diameteraperture. It is contemplated that numerous fluid regulating microvalveassemblies can be prepared on a single substrate being formed in rowsand columns with appropriate spacing between each microvalve assembly.The microvalve assemblies can be mass produced and separated forincorporation into a cell or housing.

One or more layers are then deposited upon the substrate 62 in desiredareas thereof. Such layers can be part of the microvalve body ormicroactuator and can be conductive or non-conductive as desired. Afirst layer is deposited onto the substrate 62. The first layerdeposited onto the substrate 62 can be a conductive layer 64, depositedin two lines, each of which form an electrical lead, so that one end ofeach lead is adjacent an edge of the microvalve assembly. In a preferredembodiment, the conductive layer 64 is formed of two electrical leadlines which extend in a direction parallel to the length or width ofsubstrate 62.

An insulating layer 66 is then printed onto the assembly, over at leasta portion of the conductive layer 64. The insulating layer 66 generallycomprises a dielectric coating sheet or film, or the like, which iselectrically non-conductive and will not decompose, become conductive orunintentionally adhere to a subsequent layer when exposed to heating ofthe later applied resistive layer, as described below. Such insulatingcoatings are known to those skilled in the art and include, but are notlimited to, urethanes, acrylates, polysulfones, polysiloxanes,halogenated polymers, and polyesters, or combinations thereof. In oneembodiment, one or more insulating layers 66 deposited on the substrate62 or another layer, or combinations thereof, can be formed fromnon-conductive or dielectric polymers, rubbers, or elastomers asdescribed for the substrate 62 hereinabove. In FIG. 3, three insulatingsublayers are shown, but any appropriate number of layers can be used tocreate the desired form. If more than one insulating layer is used, eachlayer can be the same or a different material. In some embodiments,insulating layer 66 is chosen to provide effective parting layercharacteristics.

In a preferred embodiment as shown in FIG. 3, the insulating layer 66covers substantially all of the substrate 62 of the microvalve assemblyand the conductive layer 64 except for one or more areas near one ormore ends or edges of the substrate 62. Printing of one or moreinsulating layers, such as 66, 68, and 70 as illustrated in FIG. 3, canbe accomplished in one or more passes in order to build up theinsulating layers 66, 68, 70 on the substrate 62, such as in the areawhere the aperture will be or any other desired area. In a preferredembodiment as illustrated in FIG. 3, microvalve body insulating layer 66has a further insulating layer 68 printed on a portion thereof,generally between the lead lines of conductive layer 64. The uppersurface of insulating layer 68 is curved in order to cause resistivelayer 78 to expand away from insulating layer 68 during heating andexpansion of the resistive layer 78. The microvalve body also includesan additional insulating layer formed as a boss 70 on insulating layer68. Boss 70 is generally a raised rim surrounding aperture 72 thatserves to provide a gasket having desired sealing characteristics. Alaser or chemical etching process then is utilized to remove theportions of the insulating layer above the conductive lines of the firstlayer or any insulating layer material above aperture 72 in substrate62, and combinations thereof.

Afterwards, conductive material, which can be of the same type or adifferent type than utilized in the first layer, is deposited in theareas removed by the laser to provide rigid electrical contacts 74protruding up through the insulating layer. The composition of theconductive material of protruding electrical contact 74 is not critical,but preferably the material is of appropriate resistivity, is rigid, hasadequate cohesive strength, and is readily adhered to by the resistivelayers 78 described below. It is important, however, that the conductivematerial, if a liquid, be able to dry upon being printed or coated onthe substrate or other layer, leaving a conductive coating thereon.Examples of conductive materials include, but are not limited to, metalsand solvated polymer solutions containing conductive particles such asaluminum, carbon, silver, gold, copper, platinum, or combinationsthereof. The conductive solids content of the solvated polymer generallyranges from about 40 to about 90 percent by weight, based on the totalweight of the solvent, polymer, and conductive solids in the mixture.The amount of conductive particles required to be present in the mixtureto provide the desired electrical conductivity may vary depending on theidentity of the conductive particle due to differences among theparticles with respect to density, conductivity, etc. The same ordifferent coatings may be utilized in the same or different layers ofthe microvalve assembly. The conductive material may be comprised of avariety of film forming polymers which are compatible with theconductive particles and mixed therewith and which will adhere to thesubstrate or other layer upon drying or removal of the solvent. Examplesof film forming polymers which may be utilized to form a conductivematerial include, but are not limited to, polymers such as polyestersand polyacrylates. One of ordinary skill in the art can readilyascertain the identity of acceptable polymers for use in the conductivematerial layer(s). Alternatively, direct metal deposition byelectrochemical or vapor deposition means could be employed alone, or incombination with the above polymer matrix films to form eitherconductive layer 64 or conductive protruding electrical contact 74, andcombinations thereof.

An aperture or apertures 72 are left uncoated or created after formingthe one or more insulating layers 66, 68, and 70 immediately above andmatching the aperture or apertures 72 in the substrate 62, to extendthrough both the substrate and the insulating layers. A plug of materialis then placed in each aperture 72 which can be washed or melted outafter the next layer or layers have been deposited. Examples of suitablematerials include waxes and low molecular weight polymers that can be atleast partially removed. The plug is utilized to prevent subsequentmaterial applied to the microvalve assembly from obstructing orpartially obstructing aperture 72. A parting layer 76 is next printed ondesired areas of the insulating film 68, 70 so that the resistive layer78 will not adhere to the insulating film. The resistive material layer78 is deposited upon a predetermined portion of an upper surface of themicrovalve assembly, generally on the parting layer 76. The resistivematerial layer 78 is conductive and has a coefficient of thermalexpansion (CTE) greater than that of preferably all of the insulatinglayers 66, 68, 70. The resistive material layer 78 is deposited at leastin an area which makes electrical contact with the two electricalcontacts 74 protruding upward through the insulating layer 66 and alsocovers the aperture 72 in the insulating layers 66, 68 and 70. A segmentof a circuit is formed running from the first lead through the resistivematerial layer 78 to the second lead. The resistive material layer 78 issecured to the microvalve assembly in at least one location. The plug ofmaterial is removed from aperture 72 after the resistive material layer78 is formed. Upon the application of a potential to the resistivematerial layer 78 through the electrical leads 74 or contacts 64 of theconductive layers, the resistive material layer 78 heats and distortsaway from the insulating layers 68, 70, creating a passage between theresistive material layer 78 and insulating layer 68, 70 having partinglayer 76 thereon to the aperture or apertures 72 in the insulating layerand substrate through which fluid can pass. The substrate 62 insulatinglayers 66, 68 and 70, and parting layer 76 of the microvalve body remainstationary while the microactuator comprising resistive material layer78 moves from a first position to a second position, thereby opening themicrovalve of the microvalve assembly thereby permitting fluid flowthrough aperture 72. Examples of resistive materials include, but arenot limited to, materials described for the conductive layers 64 and 74hereinabove, and preferably are high thermal expansion conductivepolymer matrix materials including conductive particles, and highthermal expansion metals such as aluminum, certain brasses, bronzes andmagnesium.

The microvalve assembly optionally contains a cover layer (not shown inFIG. 3) which is preferably non-conductive and is formed having a cavityto accommodate the distorting resistive material layer 78. The coverlayer preferably includes at least one aperture to allow for flow offluid into or out of the passage between the resistive material layer 72and insulating layers 68, 70 when the resistive microactuator is in thesecond (open) position. Alternatively, cover layers are generally notutilized when space is available for the microvalve microactuatorcomprising the resistive material layer 78 to deform away from themicrovalve aperture 72 to allow flow of fluid.

The above described fluid regulating microvalve assembly is optionallydetached from the substrate 62 and assembled into a cell as desired tocontrol flow of fluid. That said, if the substrate 62 is removed,insulating layer 66 is generally considered the base of the microvalvebody of the microvalve assembly.

In an alternative embodiment, the resistive material layer can be amulti-layer material, as described below for the embodiment shown inFIGS. 4A and 4B.

The fluid regulating microvalve assembly optionally includes a latch.FIGS. 4A and 4B show an embodiment of a microvalve assembly with a latchin a closed position and an open position, respectively. A control unit,which can include a microchip or imbedded microcircuit, as shown in FIG.5, can be added to keep the microvalve open without expenditure ofparasitic power. The control unit can be connected electrically throughtwo additional conductive contact lines included in the conductive layerof the microvalve assembly, extending across at least part of thesubstrate to provide electrical connections to the latching mechanism.The control unit can be used to provide power to the latching mechanismonly when power is required from the cell or battery for a poweredappliance.

The latching mechanism includes a multi-layer actuator, or latch arm,made from resistive material that will heat and bend when current passesthrough it. In FIG. 4A, latch arm 82 is shown in a first position whenthe microvalve is in the closed position. Upon application of apotential across the latch arm 82, through conductive strips 84connected to opposite sides of the latch arm 82, the latch arm 82 heats,causing it to bend up and to the left. At the same time, a potentialapplied across the resistive layer 78 through conductive strips 64,causing the resistive layer 78 to expand and move upward with partinglayer 76, beyond the level shown in FIG. 4B, thereby allowing the latcharm 82 to move past a downward projection 90 from the parting layer 76.The potential is then removed from the resistive layer 78, allowing itto cool and move downward slightly, into the position shown in FIG. 4B,where the parting layer 76 and resistive layer 78 are held in thisposition by the latch arm 82. Once the projection 90 has moved downward,it will retain the latch arm 82 in its second position as shown in FIG.4B, so the potential across the latch arm 82 can be removed and thelatch arm 82 will hold the microvalve in the open position shown in FIG.4B, providing a passageway through which fluid can pass to the aperture72 in the substrate 62 and insulating layer 66, 68, 70, even though nocurrent is flowing through the resistive layer 78 or the latch arm 82.The microvalve is connected to a control unit, and when the control unitsenses that power is no longer required from the cell, the control unitallows a potential to be placed across the resistive layer 78 throughconductive strips 64 for a sufficient time for the resistive layer 78and parting layer 76 to move upward slightly so the projection 90 nolonger retains the latch arm 82. The latch arm 82 returns to its firstposition, allowing the parting layer 76 and resistive layer 78 to returnto their first position after the potential is removed from theresistive layer 78 and the resistive layer 78 cools. In this manner,power from the cell is consumed only to move the microvalve from theclosed position (FIG. 4A) to the open position (FIG. 4B) and vice versa,and the useful life of the cell is extended.

The microvalve assembly in FIGS. 4A and 4B can be made utilizing aprocess similar to that described above for the microvalve assembly inFIG. 3, except as follows. Two additional conductive strips 84 aredeposited on the bottom surface of the substrate 62. A hole is also madein the substrate 62 through which the latch arm 82 can be inserted. Thehole can be angled so the latch arm 82 will be at an acute angle to theupper surface of the substrate 62 as shown in FIG. 4A. A portion ofinsulating sublayers 66 and 68 is removed (alternatively sublayers 66and 68 are deposited in such a way that they do not completely cover thesubstrate 62) so there is a cavity 92 in the sublayers 66 and 68 abovethe latch arm hole in the substrate 62 into which the latch arm 82 canextend. The cavity 92 is large enough to allow the latch arm 82 to movebetween its first and second positions, and the hole and cavity 92 arelocated such that, when the latch arm 82 is inserted, each of twoopposing surface layers (described below) is near one of the conductivestrips 84. The latch arm 82 is inserted through the latch arm hole soits distal end extends into the cavity 92 in sublayers 66 and 68. Afterthe latch arm 82 is inserted through the substrate 62, electricalconnections are made between each of the opposing surface layers of thelatch arm 82 and the adjacent conductive strips 84. This can be done byapplying an electrically conductive material 94, which can be aconductive adhesive that also secures the end of latch arm 82 inposition within the latch arm hole. The hole can filled in around thelatch arm 82 with a nonconductive material to help hold the latch arm 82in place and prevent fluid from flowing through the latch arm hole. Adownward protrusion 90 can be added to the parting layer 76.

The latch arm 82 can be a multi-layer component, having high- andlow-CTE sublayers, similar to the multi-layer resistive layer 78 shownin FIGS. 4A and 4B and described below. Preferably it has threesublayers—a high-CTE material sublayer, a low-CTE material sublayer, anda sublayer of nonconductive material therebetween except at its distalend. At the distal end the resistive material layers are in directcontact to provide a complete electrical path through the latch armbetween the points of electrical contact with the conductive strips 84at the opposite end of the latch arm 82.

In an alternative method of making a microvalve with a latch mechanismthe latch arm is deposited within the cavity in the insulating layer;e.g. by depositing layers of the latch arm and parting layers, using aprinting process for example. This can eliminate the need to make a holein the substrate for inserting the latch arm, a separate latch arminsertion process and subsequent filling of the hole around the insertedlatch arm. After forming a cavity for the latch arm in the substrate, aparting layer is deposited over portions of the substrate and conductiveleads so the latch arm will not adhere thereto, except as desired at oneend of the latch arm to secure that end to the substrate and make theproper electrical contacts with the conductive leads. Strips of thehigh-CTE layer, nonconductive layer and low-CTE layer of the latch armare sequentially deposited to form the latch arm, with one end of thehigh-CTE layer adhered to one of the conductive strips, thenonconductive layer covering the high-CTE layer except at the oppositeend, where the low-CTE layer is adhered to the exposed end of thehigh-CTE layer. The low-CTE layer also extends beyond the end of thehigh-CTE layer and is adhered to the other conductive strip to create anelectrical path from the one electrical contact strip and through thehigh-CTE layer and the low-CTE layer to the other electrical contactstrip. A second parting layer can then be deposited over the completedlatch arm if necessary to prevent the latch arm from adhering to othercomponents of the microvalve assembly with which it may come in contact.In such an embodiment, it may be desirable to provide an angled surfaceonto which the latch arm is deposited, rather than depositing itdirectly onto the flat substrate, in order to optimize the placement ofthe latch arm to move from its first position to an optimal (e.g.,vertical) second position.

In the embodiment of a microvalve assembly shown in FIGS. 4A and 4B, theresistive layer 78 includes two sublayers, a low-CTE sublayer 86,disposed adjacent to the parting layer 76, and a high-CTE sublayer 88,disposed above the low-CTE sublayer 86. The low-CTE sublayer 86 is madefrom material with a low CTE, such as glass, silicon or INVAR® (an ironalloy comprising about 36 weight percent nickel). The high-CTE sublayer88 can be made from material with a high CTE, such as those describedabove for single layer resistive layer. Such a multi-layer structure mayproduce greater vertical movement to provide a larger fluid passageway.The embodiment shown in FIGS. 4A and 4B also shows the resistive layer78 being thinner at its edges. This can make the resistive layer 78 moreflexible at the edges, so the thin peripheral area acts as a hinge.

In alternative embodiments to the microvalve assemblies in FIGS. 3, 4Aand 4B, the parting layer 76 can be made from a material that willadhere to the insulating layer 68 and not to the resistive layer 78. Inthese embodiments, aperture 72 and the latch arm cavity 92 would extendthrough the parting layer 76 as well, to provide a fluid passagewaybetween the resistive layer 78 and the parting layer 76 to the aperture72.

A further embodiment of fluid regulating microvalve assembly isillustrated in cross section in FIG. 6. The cross-section shows amicrovalve assembly in two sections which are in position to beconnected, such as through an adhesive or lamination, or the like, tocreate an assembled microvalve assembly. The microvalve assemblyincludes a microvalve body comprising substrate 36 which is preferablyin the form of a rigid sheet or film, as described hereinabove.Substrate 36 includes aperture 37. End supports 38 are deposited onsubstrate 36, preferably utilizing a printing process. Boss 48 can bedeposited around aperture 37 utilizing the same material as end supports38. If desired, end supports 38 and boss 48 can be deposited as acontinuous layer on the substrate 36 and portions of the materialsubsequently removed to create the end supports 38 and boss 48.Preferably boss 48 is a different material, selected to provide a goodseal with boss 46. Alternatively, a coating could be deposited on thesurface of at least one of boss 48 and boss 46 to function as a gasket.

The upper portion of the microvalve assembly comprising a microactuatoras illustrated in FIG. 6 is formed on a non-conductive membrane sheet40, at least utilizing the printing process. In one embodiment, themembrane sheet 40 is formed of material as described for the substratehereinabove, such as polymer matrix semiconductors, glasses, silicon,polymers, rubbers, or elastomers. Selected areas of the membrane sheet40 are overprinted in one embodiment with a non-conductive layer 49,preferably adjacent to two opposite ends of the membrane sheet 40 atleast in the area above end supports 43, with the same or a differentmaterial as membrane sheet 40 in order to create a relatively thinsection within supports 43, located radially outward from the locationof boss 46. An expansion layer 41, which includes a resistive material,is deposited on membrane sheet 40 preferably by printing. In thisembodiment, expansion layer 41 is preferably formed in an annular stripdisposed around boss 48, rather than having a planar shape as in theembodiment shown in FIGS. 4A and 4B. Conductive leads make electriccontact between each of contact points 44 and 45 and expansion layer 41,such as illustrated. Upon application of a potential to the contactpoints 44 and 45, expansion layer 41 heats, expands, and causesdeformation of membrane sheet 40. Aperture 39 is preferably placed inmembrane sheet 40 to admit fluid to the center of the microvalve. A boss46 is deposited on the underside of membrane sheet 40 in one embodimentand is sufficient in size and located to cover boss 48 in the lowerportion of the microvalve assembly. Boss 46 functions as a sealing plugon lower annular boss 48. End supports 43 are deposited along one ormore lower edges of the membrane sheet 40. Boss 46 and end supports 43can be deposited utilizing a printing process. If desired, end supports43 and boss 46 can be deposited as a continuous layer on the undersideof membrane sheet 40 and portions of the material subsequently removedto create the end supports and boss 46.

As stated hereinabove, the upper and lower end supports are connected toform the microvalve assembly. The supports can be connected vialamination or an adhesive such as known in the art. Optionally, a gasketor sealant layer is deposited on boss 48 to optimally seal aperture 37in conjunction with boss 46. The gasket or sealant layer is preferablyformed of an elastomeric compound which will not adhere to the layer,such as boss 46 contacting it during the operation of the microvalve andmicroactuator. Suitable materials include, but are not limited to,polyethylene terephthalate, polytetrafluoroethylene such as TEFLON®(DuPont), or polymethylsiloxane. In an open position, fluid can flowthrough the gap in the sides of the microvalve if not sealed by endsupports 38 and 43, or through aperture 39 if the microvalve ends aresealed, and ultimately through aperture 37 into the cell or into abattery compartment. If desired different portions of a layer (e.g., endsupports 38 and boss 48 on substrate 36, or end supports 43 and boss 46on membrane sheet 40) can be either the same material, as describedabove, or they can contain different materials.

The embodiment shown in FIG. 6 can be modified to incorporate a latchmechanism, which can be controlled by a control unit. For example, asshown in FIG. 7, a latch arm 82 is inserted through a hole in thesubstrate 36, in a manner similar to that described above for theembodiment shown in FIGS. 4A and 4B. A downward projection 90 can bedeposited on the underside of the membrane sheet 40 to retain the latcharm 82 in its second position to hold the microvalve in an openposition. In this embodiment, conductive strips 84 are deposited on thetop surface of the substrate 36, but they could be located on the bottomsurface, as shown in the embodiment in FIGS. 4A and 4B. If theconductive strips 84 are on the top surface of the substrate 36,electrical connections to a control unit could be provided, for examplein a manner similar to that described above for making electricalconnections between the lead lines of conductive layer 64 and theresistive layer 78 in the microvalve assembly shown in FIGS. 4A and 4B.

FIG. 5 is a schematic diagram illustrating one embodiment of a controlcircuit for microactuator 50 of a microvalve assembly of the presentinvention. Microactuator 50 is connected to a control unit 54, that canbe printed in one embodiment, connected in series with an electricalswitch 52. FIG. 5 also illustrates load 51, connected in series withswitch 52, control unit 54 and battery 53. Control unit 54 responds tovoltage and current characteristics of the circuit it is connected to.Control unit 54 can vary the potential supplied to the microactuator 50in order to regulate or optimize fluid flow through the microvalveassembly.

The fluid regulating microvalve assemblies of the present inventioninclude microactuators that can move in various ways and in combinationsof ways from a first position where fluid cannot pass through themicrovalve body aperture to at least a second position which allowsfluid to pass through the microvalve body aperture. Movements include,but are not limited to, motion towards and away from a portion of themicrovalve body particularly an aperture, linear or non-linear movement,movement parallel to a surface such as a microvalve body, and movementwhich serves to engage or disengage a latch.

In one embodiment the fluid regulating microvalve assembly iselectrically connected, preferably in a series circuit, to the cell itis controlling fluid access thereto. In a further embodiment, the fluidregulating microvalve assembly is provided with a separate power sourceother than the cell or cells it is operatively connected to. Electricalconnections between the microvalve assembly electrical contacts and thecell electrodes can be accomplished in any suitable manner that providesa reliable connection. For example, one of the microvalve assemblyelectrodes can be in direct physical and electrical contact with thepositive electrode such as the oxygen reduction electrode.Alternatively, one electrical contact can be in direct contact with anelectrically conductive portion of the cell housing that is inelectrical contact with the positive electrode. Further, if desired, anelectrical lead can be used to provide electrical contact with thepositive electrode.

The microvalve assembly electrical contact that is electricallyconnected to the negative electrode of the cell can be connected with anelectrical lead. An electrical lead can have a travel path around orthrough the positive electrode or oxygen-reduction electrode, as long asthe lead is electrically insulated therefrom. In one embodiment, theelectrical connector connecting the microvalve assembly to the negativeelectrode of the cell may be in the form of a wire or thin metal stripwith dielectric material insulating any parts of the lead that mayotherwise come in electrical contact with the positive electrode, eitherdirectly or indirectly through another cell component such as aconductive portion of the cell housing, a positive electrode, currentcollector, or a positive electrode electrical contact, lead or spring.In a further example, the electrical lead to the negative electrode maybe in the form of one or more thin layers of metal printed or otherwisedeposited on a portion of one or more other cell component, such assurfaces of gasket, insulators, cans, covers, and the like. Layers ofthe dielectric material may be coated over or beneath, or a combinationthereof, the metal layers to provide the necessary insulation from thepositive electrode.

The potential applied to the fluid regulating microvalve assembly tooperate the microactuator can originate within the cell. For example,the potential applied to the microvalve assembly can be the cellpotential, as described above. The cell potential can also be changed.If a higher voltage is needed to produce a desired microvalve assemblymicroactuator movement, the cell potential can be adjusted upward.Adjusting the cell potential can allow for the use of different types ofmaterials for the microactuator. Increasing the cell potential can beaccomplished, for example, with a controlled circuit, to regulate orstep up the cell voltage and thus more strongly induce movement of themicroactuator to operate the microvalve assembly.

The control circuit can also be utilized to control other cell featuresor components. For example, the control circuit can be utilized tomonitor the need for oxygen and then apply a potential across themicrovalve assembly to open or close the microactuator. For example, thecontrol circuit can include an oxygen sensor to monitor the oxygen levelin the cell. The control circuit can also be utilized to monitor thecell voltage or monitor the potential of the positive electrode againsta separate reference electrode. The control circuit can be printedutilizing the printing process of the present invention or anotherprocess. The control circuit can be applied to a cell or batterycomponent or be included on a separate substrate or wafer or chip, orany other suitable arrangement can be utilized.

The control circuit can have components including, but not limited to,fuses, inductors, capacitors, resistors, and transistors. The controlcircuit can be designed to fail on contact with a corrosive fluid orshut down upon excessive current demand.

The fluid regulating microvalve assemblies of the present invention canbe incorporated into cells in various ways, depending on the type anddesign of the microvalve assembly and the cell. In one embodiment asdescribed hereinabove, the fluid regulating microvalve assembly iscontained within the cell housing. However, it is to be understood, thatother embodiments of the invention are contemplated in which themicrovalve assembly, control circuit, or combinations thereof, can bedisposed outside the cell, such as between the external surface of thecell housing and a battery jacket or case. The minimal volumerequirements for the fluid regulating microvalve assembly make suchembodiments possible in batteries with little space available betweenthe cell and jacket or case.

As disclosed above, a preferred embodiment of an electrochemical cellusing a microvalve assembly according to the invention is anair-depolarized cell. Another preferred embodiment is an air-assistedcell. Yet another preferred embodiment is a fuel cell. A preferred cellshape is a button shape. Another preferred cell shape is a cylindricalshape. Yet another preferred cell shape is a prismatic shape.

An electrochemical cell according to the invention can be part of abattery comprising one or more cells. In one preferred embodiment morethan one battery cell can share a single microvalve assembly, and inanother preferred embodiment each cell can have a separate microvalveassembly. In other preferred embodiments, microvalve assemblies can belocated within or on the battery housing, or they can be mounted on aportion of an appliance in which the battery is installed. Similarly, inone preferred embodiment more than one cell can share the same controlunit, and in another preferred embodiment each cell can have a separatecontrol unit. In other preferred embodiments, control units can belocated within on or on the battery housing, or at least portions of thecontrol units can be mounted on a portion of an appliance in which thebattery is installed.

It will be understood by those who practice the invention and thoseskilled in the art that various modifications and improvements may bemade to the invention without departing from the spirit of the disclosedconcept. The scope of protection afforded is to be determined by theclaims and by the breadth of interpretation allowed by law.

1. An electrochemical cell, comprising: a housing comprising one or more fluid inlet apertures, a negative electrode, a fluid consuming positive electrode, and a microvalve assembly operatively connected to the one or more fluid inlet apertures for controlling passage of fluid to the fluid consuming positive electrode, wherein the microvalve assembly comprises; (a) a stationary microvalve body comprising a polymer, elastomer or rubber and an aperture located between a first surface and a second surface; (b) a movable microactuator connected to the microvalve body and capable of moving between a first position where fluid cannot pass through the microvalve body aperture and a second position which allows fluid to pass through the microvalve body aperture; and (c) a segment of a circuit extending from a first lead located on the microvalve body to a resistive material layer of the movable microactuator to a second lead of the microvalve body.
 2. The electrochemical cell according to claim 1, wherein the microactuator moves away from the microvalve body in moving from the first to the second position, and the microactuator moves toward the microvalve body in moving from the second to the first position.
 3. The electrochemical cell according to claim 1, wherein at least one of the microvalve body and the microactuator comprises a printed layer.
 4. The electrochemical cell according to claim 1, wherein the microvalve assembly includes a control unit that is adapted to monitor a fluid level within the housing and is able to apply a potential across the microvalve assembly.
 5. The electrochemical cell according to claim 1, wherein the microvalve assembly is operatively connected between the one or more fluid entry apertures and the fluid consuming positive electrode.
 6. The electrochemical cell according to claim 1, wherein the cell is an air depolarized cell, an air-assisted cell, or a fuel cell.
 7. The electrochemical cell according to claim 1, wherein the cell is a button cell, a cylindrical cell, or a prismatic cell.
 8. The electrochemical cell according to claim 1, wherein the microvalve body includes a substrate and an insulating layer printed on at least a portion of the substrate.
 9. The electrochemical cell according to claim 1, wherein the microactuator comprises a resistive material layer.
 10. The electrochemical cell according to claim 9, wherein the resistive material layer comprises metal or a polymer containing conductive particles.
 11. The electrochemical cell according to claim 1, wherein the resistive material layer heats and distorts away from the microvalve body aperture to the second position when a potential is applied between the first lead and the second lead.
 12. The electrochemical cell according to claim 1, wherein the microvalve assembly includes a latch operatively connected to the microvalve body.
 13. The electrochemical cell according to claim 1, wherein the microvalve assembly includes an integrated control unit capable of controlling the movement of the microactuator between the first position and the second position.
 14. The electrochemical cell according to claim 1, wherein the movable microactuator is operatively connected to the microvalve body through one or more printed supports, and wherein the movable microactuator comprises a membrane sheet and a resistive material layer printed on the membrane sheet.
 15. The electrochemical cell according to claim 14, wherein the microactuator includes a boss connected to a bottom side of the membrane sheet that seals the microvalve body aperture in the first position to prevent fluid flow through the microvalve body aperture.
 16. The electrochemical cell according to claim 14, wherein the movable microactuator includes a segment of a circuit extending from a first lead to the resistive material layer to a second lead, and wherein a potential applied between the first lead and the second lead causes distortion of the microactuator and movement from the first position to the second position. 